Fluid delivery mechanism

ABSTRACT

The present invention provides an infusion pump  10  for providing a flow of a liquid through an tube  28 . The infusion pump  10  includes at least two occluders  152, 162  having an open position and a closed position for releasably pinching-off the tube  28 . A metering chamber is disposed between the two occluders  152, 162 . A first plunger  72  and a second plunger  73  are provided, each plunger  72, 73  having an open position and a closed position for releasably compressing the metering chamber. In the method of the present invention, an occluder  152  releasably pinches-off the tube near the source of the liquid at a first location. The second occluder  162  releasably pinches-off the tube at a second location that is downstream from the source of the liquid  23  and the first location. The tube  28  is released at the first location and a plunger  72  compresses the tube  28  between the first location and the second location, thereby generating a flow of the liquid through the tube  28  in a direction towards the source of liquid  23.

FIELD OF THE INVENTION

[0001] The present invention relates to a fluid delivery mechanism forthe delivery of liquids and other fluids.

BACKGROUND OF THE INVENTION

[0002] Fluid delivery mechanisms are known in the art. Positivedisplacement pumps are one category of fluid delivery mechanisms thatoperate on a flexible tube to generate a pumping action. One category ofpositive displacement pumps that operate on the flexible tube are alsoknown as valve-type pumps. In the operation of the valve-type pump, aplunger compresses the flexible tube thus forcing a liquid contained inthe flexible tube out of the flexible tube.

[0003] One such application for the positive displacement pump is theadministration of intravenous liquids. The administration of intravenousliquids to a patient is well known in the art. Typically, a solutionsuch as saline, glucose or electrolyte contained in a flexible containeris fed into a patient's venous system through a conduit such as apolyvinyl chloride (PVC) tube which is accessed to the patient by acatheter. Many times, the fluid is infused under the forces of gravity,and the rate of flow is controlled by a roller clamp which is adjustedto restrict the flow lumen of the tube until the desired flow rate isobtained.

[0004] Flow from the container to the patient also is known to beregulated by means other than a roller clamp. It is becoming more andmore common to use an electronically controlled infusion pump. Suchpumps include, for example, valve-type pumps. In such devices, acontainer or bag typically provides for the delivery of the fluid to thetube. A mechanism pinches on the tube using an occluder, and typically apair of occluders. A plunger, pressing on the tube between the occludersprovides the motive force to deliver fluid to the patient. When fluid isdelivered to a patient, one of the occluders opens. Different bolussizes are accomplished by controlling a stroke distance of the plunger.Different flow rates are accomplished by varying the frequency of theoperation of the occluders and plungers open/close cycle.

[0005] One disadvantage of the prior art infusion pumps is that theoperation of an occluder and/or a plunger on the tube will eventuallydeform the tube and change the pumping volume. This disadvantage mayarise for many reasons. The operation of the occluder or the plunger maystretch the tube thus changing the volume contained within the tube. Theoperation of the occluder or the plunger may cause the tube topermanently set in a shape that also results in a changed volumecontained within the tube. Therefore, over time, such devices becomeless accurate as to the amount of liquid delivered to a patient. Whilemechanical devices have been designed that return the tube to itsoriginal shape between pumping cycles, such devices do not completelyeliminate the inherent inaccuracy in the valve-type pumps.

[0006] What is needed is a medical infusion pump which improves theaccuracy of valve-type pumps. What is also needed is a medical infusionpump that does not lose accuracy of bolus delivery the more times thepump is used. What is further needed is a medical infusion pump thatoffers these advantages yet uses standard tubing and is readilyadaptable for use in multiple clinical settings

SUMMARY OF THE INVENTION

[0007] The present invention provides a fluid delivery mechanism whichimproves the accuracy of valve-type pumps. The present inventionprovides a fluid delivery mechanism that does not lose accuracy of bolusdelivery the more times the pump is used. The present invention providesa fluid delivery mechanism that controls the shape of the tubingthroughout the pump cycle. The present invention also provides a fluiddelivery mechanism that is readily adaptable to use in multiple clinicalsettings. The present invention further provides a fluid deliverymechanism that is readily adaptable to multiple pump settings.

[0008] The present invention provides a fluid delivery mechanism forproviding a flow of a deliverable fluid through a tube. Examples of thedeliverable fluid are a liquid and a medical liquid. The fluid deliverymechanism includes at least two occluders having an open position and aclosed position for releasably pinching-off the tube. A tube portionbetween the two occluders forms a metering chamber. A first plunger anda second plunger are provided, each plunger having an open position anda closed position for releasably compressing the metering chamber. Inthe method of the present invention, an occluder releasably pinches-offthe tube near the source of the liquid at a first location. The secondoccluder releasably pinches-off the tube at a second location that isdownstream from the source of the liquid and the first location. Thetube is released at the first location and a plunger compresses the tubebetween the first location and the second location, thereby generating aflow of the liquid through the tube in a direction towards the source ofliquid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is an example of an intravenous fluid infusion pump inwhich the present invention can be utilized.

[0010]FIG. 2 is a perspective view of the intravenous fluid infusionpump of FIG. 1 in an open position.

[0011]FIG. 3 is an exploded view of the intravenous fluid infusion pumpof FIG. 1 illustrating components internal to the intravenous fluidinfusion pump.

[0012]FIG. 4 is a further exploded view of the intravenous fluidinfusion pump of FIG. 1 illustrating further components internal to theintravenous fluid infusion pump.

[0013]FIG. 5 is a schematic of a fluid delivery mechanism made inaccordance with the principles of the present invention.

[0014]FIG. 6 is a plan sectional view of an occluder mechanism made inaccordance with the principles of the present invention that utilizes asingle plunger.

[0015]FIG. 7 is an elevation sectional view of the occluder mechanism ofFIG. 6.

[0016]FIG. 8 is an elevation sectional view taken along axis A-A of FIG.6.

[0017]FIG. 9 is an elevation sectional view taken along the B-B axis ofFIG. 6.

[0018]FIG. 10 is an elevation sectional view taken along the C-C axis ofFIG. 6.

[0019]FIG. 11 is an elevation sectional view taken along the D-D axis ofFIG. 6.

[0020]FIG. 12 is a sectional view of the downstream occluder of FIG. 6taken along axis E-E of FIG. 6.

[0021]FIG. 13 is a sectional view of the upstream occluder of FIG. 6taken along axis F-F of FIG. 6.

[0022]FIG. 14 is a diagram of a system in accordance with the principlesof the present invention.

[0023]FIG. 15 is a schematic of a valve/occluder/plunger arrangement inaccordance with the principles of the present invention.

[0024]FIG. 16 is an operating profile diagram of thevalve/occluder/plunger arrangement of FIG. 15.

[0025]FIG. 17 is a schematic of an alternative embodiment of avalve/occluder/plunger arrangement in accordance with the principles ofthe present invention.

[0026]FIG. 18 is an operating profile diagram of thevalve/occluder/plunger arrangement of FIG. 17.

[0027]FIG. 19 is a schematic of an alternative embodiment of a fluiddelivery mechanism made in accordance with the principles of the presentinvention that utilizes two plungers.

[0028]FIG. 20. is a plan sectional view of an alternative embodiment ofan occluder mechanism made in accordance with the principles of thepresent invention utilizing two plungers.

[0029]FIG. 21 is an elevation sectional view of the occluder mechanismof FIG. 20.

[0030]FIG. 22 is an elevation sectional view taken along axis A-A ofFIG. 20.

[0031]FIG. 23 is an elevation sectional view taken along the B-B axis ofFIG. 20.

[0032]FIG. 24 is an elevation sectional view taken along the C-C axis ofFIG. 20.

[0033]FIG. 25 is an elevation sectional view taken along the D-D axis ofFIG. 20.

[0034]FIG. 26 is a schematic of a dual plunger arrangement in accordancewith the principles of the present invention.

[0035]FIG. 27 is an operating profile diagram of a high volume infusionof the dual plunger arrangement of FIG. 26.

[0036]FIG. 28 is an operating profile diagram of a medium volumeinfusion of the dual plunger arrangement of FIG. 26.

[0037]FIG. 29 is an operating profile diagram of a low volume infusionof the dual plunger arrangement of FIG. 26.

[0038]FIG. 30 is an alternate embodiment of a fluid delivery mechanismmade in accordance with the principles of the present invention thatutilizes a cam-actuated mechanism.

[0039]FIG. 31 is a cross-sectional view of the cam shaft of FIG. 30.

[0040]FIG. 32a is an operating profile diagram of the occluder mechanismof FIG. 30.

[0041]FIG. 32b is an operating profile diagram of the occluder mechanismof FIG. 30 illustrating the relationship of a cam angular position witha position of an occluder and a plunger.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0042] Referring to FIG. 1, an example of a fluid delivery device inwhich the present invention can be utilized is referred to generally as210. While the example described herein is an ambulatory intravenousinfusion pump, the principles of the present invention can be applied toa number of different fluid delivery environments. The pump 210 includesa main body portion 214 and at least one fluid delivery mechanism 216.The pump 210 also includes a cover 212.

[0043] Referring to FIG. 2, the pump 210 of FIG. 1 is seen in the openposition. At least one fluid delivery mechanism 216 is located withinthe main body 214 of the pump 210. The fluid delivery mechanism 216includes a tube-loading channel 228 into which a tube 28 is loaded intothe pump 210. The fluid delivery mechanism 216 may further include atube-loading feature. Associated with the fluid delivery mechanism 216is a bottom plate 229. Associated with a cover 212 is a top plate 227.Disposed on the bottom plate 229 are receiving mechanisms 281, 283.Disposed on the top plate 227 and operatively associated with receivingmechanisms 281, 283 are latching mechanisms 291, 293.

[0044] Referring now to FIG. 3, an exploded view of the pump 210 of FIG.1 is depicted. The pump 210 further includes a pad 216 disposed on thecover 212, the pad 216 providing keypad access to the pump 210. A windowis provided in the pad 216 for a display 217. In the preferredembodiment, the display 217 can be an LCD display. The pump 210 includesan electronic control 230 for controlling the operation of the pump 210.An occluder mechanism 240 is disposed within the pump 210, the occludermechanism 240 providing the means to move a fluid through the tube 228,as described in detail below. A power supply 232 is also disposed in thepump 210, the power supply 232 providing a source of power to operatethe pump 210. In the preferred ambulatory embodiment described herein,the power supply 232 is a series of batteries. Included in the occludermechanism 240 are solenoid valves 242, 243, 244 and 245. The functionsof the solenoid valves 242, 243, 244 and 245 are described in moredetail below.

[0045] Referring to FIG. 4, an exploded view of the pump 210illustrating components internal to the pump 210. The pump 210 furtherincludes occluders 252, 262 and plungers 272, 273. The function ofoccluders 252, 262 and plungers 272, 273 are described in further detailbelow.

[0046] Referring now to FIG. 5, a schematic of a fluid deliverymechanism made in accordance with the principles of the presentinvention is seen. A flexible fluid container 23 is provided filled witha liquid and connected to the tube 28. The fluid container 23 is loadedinto a chamber in the fluid delivery device (not shown). In oneembodiment, the container 23 may be optionally placed between a fixedplate 22 and an inflatable bladder 24. On the outside of the inflatablebladder 24 a restraint 26 is provided. The purpose of the restraint 26is to limit the inflation of the bladder 24 so that the bladder 24pushes against the container 23 upon inflation. The bladder 24 can be afluid-actuated chamber.

[0047] When the tube 28 is loaded in the fluid delivery device, asegment of the tube 28 is pre-compressed between a first fixed plate 75and a plunger 73. The tube 28 is pre-compressed to a non-occludedposition. Two occluders 152, 162 are provided with one on each side ofthe plunger 73 to pinch-off the tube 28. A metering chamber is disposedbetween the occluders 152, 162. The occluder that is located on thefluid container 23 side of the plunger 73 is referred to as the upstreamoccluder 152 and the other occluder is referred to as the downstreamoccluder 162.

[0048] The pre-compression of the tube 28 results in an approximatelyoval cross-sectional shape for an otherwise round tube. Thepre-compression of the tube also produces a partial vacuum in the tube.By pre-compressing the tube into an approximately oval cross-sectionalshape, the bolus volume deliverable per unit stroke distance of theplunger 73 is greater than the bolus volume deliverable without the useof the pre-compression. Furthermore, the pre-compression of the tubemaintains the tube in a pre-stressed condition thus providing a force toreturn the tube to the shape the tube accepted due to thepre-compression after the further compression of the tube by the plungerhas been released. Additionally, the pre-compression prevents an overextension of the tube during the generation of a flow of a liquidthrough the tube in a direction towards the source of the liquid. Eachof these aspects of the pre-compression are explained in further detailbelow.

[0049] The largest bolus volume achievable may be described by thefollowing equation: $\begin{matrix}{V_{b} = {\left( {V_{d}/T} \right)/\left( {N_{c}/T} \right)}} \\{{{= {V_{d}/N_{c}}};{where}},} \\{{V_{b} = {{bolus}\quad {volume}}};} \\{{V_{d} = {{{lowest}\quad {flow}\quad {rate}} - {{delivered}\quad {volume}}}};} \\{{T = {{time}\quad {over}\quad {which}\quad {the}\quad {bolus}\quad {volume}\quad {is}\quad {delivered}}};{and}} \\{N_{c} = {{number}\quad {of}\quad {delivery}\quad {{cycles}.}}}\end{matrix}$

[0050] It is generally desirable that the bending radius that the tuberealizes as a result of the pre-compression should be equal to orgreater than the wall thickness of the tube. This is to minimize thestresses realized by the tube during the pre-compression that may causea reduction in the flexural modulus of the tube. Applying this radiuslimitation, the maximum stroke distance of the plunger is defined asfollows:

[0051] St_(max)=ID_(min)−2W_(max); where

[0052] St_(max)=maximum stroke distance;

[0053] ID_(min)=minimum inside diameter of the tube; and

[0054] W_(max)=maximum wall thickness of the tube.

[0055] The theoretical bolus volume can be defined as a function of thetube length residing between the upstream and downstream occluders andthe tube diameter as the diameter changes during the delivery of thebolus volume. Accordingly, the bolus volume may be defined as follows:$\begin{matrix}{{V_{b} = {V_{o} - V_{r}}};{where}} \\{{V_{b} = {{the}\quad {bolus}\quad {volume}}};} \\{{V_{o} = {{the}\quad {original}\quad {volume}\quad {of}\quad {the}\quad {tube}}};} \\{V_{r} = \quad \begin{matrix}{{{the}\quad {volume}\quad {of}\quad {fluid}\quad {remaining}\quad {in}\quad {the}}\quad} \\{\quad {{tube}\quad {after}\quad {the}\quad {bolus}\quad {volume}\quad {is}\quad {delivered}}\quad}\end{matrix}}\end{matrix}$

[0056] V_(r) may be calculated as follows: $\begin{matrix}{{V_{r} = {V_{a} + V_{f}}};{where}} \\{{V_{a} = {{the}\quad {volume}\quad {of}\quad {an}\quad {oval}^{\prime}s\quad {arc}\quad {having}\quad {an}\quad {arc}\quad {diameter}{\quad \quad}D_{a}}};} \\{V_{a} = {\pi \quad {P_{L}\left( {D_{a}/2} \right)}^{2}}} \\{= {\pi \quad {P_{L}\left\lbrack {\left( {D_{a}/2} \right)\left( {D_{a}/2} \right)} \right\rbrack}}} \\{{= {\pi \quad {P_{L}\left\lbrack {D_{a}^{2}/4} \right\rbrack}}};{where}} \\{{P_{L} = {{the}\quad {plunger}\quad {length}}};} \\{V_{f} = {{the}\quad {volume}\quad {of}\quad {an}\quad {oval}^{\prime}s\quad {flat}\quad {segment}\quad {having}\quad a\quad {length}\quad L_{f}}} \\{{V_{f} = {D_{a}L_{f}P_{L}}};{where}} \\{{D_{a} = {{I\quad D} - S_{t}}};{where}} \\{{{I\quad D} = {{the}\quad {inside}\quad {diameter}\quad {of}\quad {the}\quad {tube}}};{and}} \\{{S_{t} = {{the}\quad {stroke}\quad {distance}\quad {of}\quad {the}\quad {plunger}}};} \\{L_{f} = {\left( {C_{i} - L_{a}} \right)/2}} \\{= {\left\lbrack {\left( {\pi \quad {ID}} \right) - \left( {\pi \quad D_{a}} \right)} \right\rbrack/2}} \\{= {\left\lbrack {{\pi \quad I\quad D} - {\pi \left( {{I\quad D} - S_{t}} \right)}} \right\rbrack/2}} \\{{= {\left( {\pi \quad S_{t}} \right)/2}};{where}} \\{{C_{i} = {{the}\quad {inside}\quad {circumference}\quad {of}\quad {the}\quad {tube}}};} \\{V_{a} = {\pi \quad {P_{L}\left( {D_{a}/2} \right)}^{2}}} \\{= {\pi \quad {P_{L}\left\lbrack {\left( {{I\quad D} - S_{t}} \right)/2} \right\rbrack}^{2}}} \\{= {\pi \quad P_{L}\left\{ {\left\lbrack {\left( {{I\quad D} - S_{t}} \right)\left( {{I\quad D} - S_{t}} \right)} \right\rbrack/4} \right\}}} \\{{= {\pi \quad P_{L}\left\{ {\left\{ {{ID}^{2} - {2{IDS}_{t}} + S_{t}^{2}} \right\rbrack/4} \right\}}};} \\{V_{f} = {D_{a}L_{f}P_{L}}} \\{= {P_{L}\left\lbrack {\left( {{ID} - S_{t}} \right){\left( {\pi \quad S_{t}} \right)/2}} \right\rbrack}} \\{= {\pi \quad {P_{L}\left\lbrack {\left( {{ID} - S_{t}} \right)\left( {S_{t}/2} \right)} \right\rbrack}}} \\\left. {= {\pi \quad {{P_{L}\left\lbrack {{IDS}_{t} - S_{t}^{2}} \right)}/2}}} \right\rbrack \\{{= {\pi \quad {P_{L}\left\lbrack {\left( {{2\quad {IDS}_{t}} - {2S_{t}^{2}}} \right)/4} \right\rbrack}}};} \\{V_{r} = {V_{a} + V_{f}}} \\\left. {= {{\pi \quad P_{L}\left\{ {\left\lbrack {{I\quad D^{2}} - {2\quad I\quad D\quad S_{t}} + S_{t}^{2}} \right\rbrack/4} \right\}} + {{\pi P}_{L}{\left\{ {{2\quad {IDS}_{t}} - {2{ST}_{2}}} \right)/4}}}} \right\} \\{= {\pi \quad P_{L}{\left\{ {\left\lbrack {\left( {{ID}^{2} - {2{IDS}_{t}} + {St}^{2}} \right) + \left( {{2\quad {IDS}_{t}} - {2{St}^{2}}} \right)} \right\rbrack/4} \right\}.}}}\end{matrix}$

[0057] Combining the terms developed above provides: $\begin{matrix}{V_{b} = {V_{o} - V_{r}}} \\{= {{\pi \quad {P_{L}\left\lbrack {{ID}^{2}/4} \right\rbrack}} - {{\pi P}_{L}\left\{ {\left\lbrack {{ID}^{2} - S_{t}^{2}} \right\rbrack/4} \right\}}}} \\{= {\pi \quad P_{L}\left\{ {\left\lbrack {{ID}^{2}/4} \right\rbrack - \left\lbrack \left( {{ID}^{2} - {S_{t}^{2}/4}} \right\rbrack \right\}} \right.}} \\\left. {= {\pi \quad {{P_{L}\left\lbrack {{ID}^{2} - {ID}^{2} - S_{t}^{2}} \right\rbrack}/4}}} \right\rbrack \\{= {\pi \quad P_{L}{S_{t}^{2}/4.}}}\end{matrix}$

[0058] Thus it can be seen that because of the pre-compression, by whichthe tube assumes an approximately oval shape, the bolus volume does notdepend on the magnitude of the inside diameter of the tube. Also,because the shape of the tube changes from round to oval, the bolusvolume does not change linearly with respect to the plunger strokedistance.

[0059] When the plunger 73 pushes on the tube 28, for a fixed strokedistance the bolus volume delivered will less when starting with a roundtube as compared to the case where an oval-shaped tube 28 is used at thestart of the plunger 73 stroke. But because the stroke distance isfixed, the energy consumed in moving the plunger over the strokedistance will be the same regardless of the starting tube shape.Therefore, pre-compressing the tube 28 results in less energyconsumption in pushing fluid through the tube 28 for a given bolusvolume. When the plunger 73 is withdrawn from pushing on the tube 28,the plunger 73 is withdrawn so that the pre-compression of the tube 28is restored. Accordingly, the tube 28 is decompressed to a secondnon-relaxed position.

[0060]FIGS. 6 through 13 depict an embodiment of an occluder mechanism40 made in accordance with the principles of the present invention. FIG.6 is a plan sectional view of the occluder mechanism 40. FIG. 7 is anelevation sectional view of the occluder mechanism 40.

[0061] The upstream occluder 152 and the downstream occluder 162 areboth spring loaded to bias the occluders 152, 162 to a closed position.The plunger 73 is spring loaded to bias the plunger 73 to an openposition. The occluders 152, 162 and the plunger 73 are each connectedto pneumatic cylinders, which are operated by compressed air andcontrolled by a controller (not shown). Each pneumatic cylinderassociated with occluders 152, 162 is preferably controlled by a 3-waysolenoid valve 43, 45, and the pneumatic cylinder associated with theplunger 73 is preferably controlled by a solenoid valve 42. The twosolenoid valves 42, 44 may be used to control the pneumatic cylinderassociated with the plunger 73, depending on the pneumatic design andthe controlled operating sequences of the occluder mechanism 40.

[0062] To ensure the tube 28 is opened and ready for delivery, thedownstream occluder 162 is open prior to the plunger 73 moving towards aclosed position. To prevent back flow, the downstream occluder 162 alsois closed before the plunger 73 returns to an open position. Theupstream occluder 152 is not opened during the downstream occluder openperiod. This method of operating sequences is designed to preventfree-flow of the fluid.

[0063] The upstream and downstream occluders 152, 162 are mechanicalvalves that open and close the fluid path between the container 23, themetering chamber, and the distal end of the tube 28. The upstream anddownstream occluders 152, 162 also allow liquid to fill the meteringchamber and escape from the metering chamber without free-flow orback-flow of the liquid.

[0064] The upstream and downstream occluders 152, 162 are normallyclosed. The upstream and downstream occluders 152, 162 pinch-off thetube 28 by a force of preferably about 2.5 pounds generated by thepre-loaded spring. Both the upstream and downstream occluders 152, 162are designed so that the pre-loaded spring force can be adjusted. Thepre-loaded spring force should be sufficient to allow the occluders 152,162 to pinch off the tube 28.

[0065] The plunger 73 is designed as a moving plate to apply pressure onthe tube 28. The plunger is preferably made of aluminum, although othermaterials, both metals and plastics, are suitable materials ofconstruction. The plate 75 is optionally configured in the shape ofchannel that operatively receives the plunger 73. The plate 75 and theplunger 73 are positioned within the occluder mechanism 40.

[0066] Likewise, the occluder mechanism 40 can be constructed ofaluminum or other suitable material. The occluder mechanism 40 isconstructed with three pneumatic cylinders incorporated for theoperation of the upstream and downstream occluders 152, 162 and theplunger 73. Each of the pneumatic cylinders associated with the upstreamand downstream occluders 152, 162 are connected directly to an in-linesolenoid valve. The plunger 73 is connected to at least one in-linesolenoid valve.

[0067]FIG. 8 presents an elevation sectional view of the occludermechanism 40 taken along axis A-A of FIG. 6. The upstream occluder 152is shown in a closed position and the plunger 73 is likewise shown in aclosed position. The downstream occluder 162 and the plunger 73 are bothshown in an opened position. The position of the solenoid valve 42,operatively associated with the plunger 73 is shown.

[0068]FIG. 9 is an elevation sectional view taken along the B-B axis ofFIG. 6. The inlet pneumatic connection 47 between the solenoid valve 42and the plunger 73 is illustrated.

[0069]FIG. 10 is an elevation sectional view taken along the C-C axis ofFIG. 6. The location of the pneumatic connection from the solenoid valve43, and from the solenoid valve 45, to the upstream occluder 152 and thedownstream occluder 162, respectively, can be seen.

[0070]FIG. 11 is an elevation sectional view taken along the D-D axis ofFIG. 6. The outlet pneumatic connection 82 between the solenoid valve 42and the plunger 73 is illustrated.

[0071]FIGS. 12 and 13 illustrate elevation sectional views of thedownstream and upstream occluders 162, 152, respectively. FIG. 12 is asection taken along axis E-E of FIG. 6, whereas FIG. 10 is a sectiontaken along axis F-F of FIG. 6. In FIG. 12, the upstream occluder can beseen in a closed position pinching-off the tube 28. In FIG. 13, thedownstream occluder 162 is shown in an opened position.

[0072] In one embodiment, a conventional commercially available aircompressor is used to provide all of the air pressure for the occludermechanism 40 and the bladder 24. Alternately one air compressor may beused to provide air pressure to the bladder 24, and a second aircompressor may be used to provide air pressure to the occluder mechanism40. A plurality of air compressor may also be used.

[0073] Referring now to FIG. 14, a diagram of a system in accordancewith the principles of the present invention is seen. The systemutilizes a fluid compressor 39. A power supply 32 provides power to avalve control 35. The valve control 35 controls a bladder control valve31. The bladder control valve 31 provides compressed air to the bladder24, which in turn presses upon the container 23 to create a source ofpressurized liquid.

[0074] The power supply 32 also provides power to a control 33 and tothe compressor 39. The control 33 controls the compressor 39 used togenerate fluid pressure to be stored in an energy storage tank 37. Theenergy storage tank 37 allows for intermittent operation of thecompressor 39, thus conserving the power supply 32. In the preferredembodiment, the fluid is air. The control 33 also controls an optionalsolenoid spike and hold circuit 36. The solenoid spike and hold circuit36 controls the solenoids that control the occluder mechanism 40. In theabsence of the spike and hold circuit 36 the control 33 directlycontrols the occluder mechanism 40. The control 33 controls the solenoidspike and hold circuit 36. The compressed air is distributed from theenergy storage tank 37 to the occluder mechanism 40, including theupstream occluder 152 and the downstream occluder 162, the plunger 73,and the bladder 24. The operation of the solenoid valves is furtherdescribed below.

[0075] The energy storage tank 37 is preferably constructed of about0.3175 cm (0.125 inch) thick welded aluminum with a capacity of about315 cm³ (19.2 cubic inches). However, other materials and methods ofconstruction and other sizes may be used. The energy storage tank 37must be constructed to safely contain the air pressure necessary tooperate the bladder 24, the upstream and downstream occluders 152, 162,and the plungers 73. The pressure may range from about 1 psig (gagepressure) to about 50 psig and preferably from about 3 psig to about 15psig. The size of the energy storage tank 37 and the air pressure can beselected to minimize the run time of the air compressor and thusconserve energy. The upstream and downstream occluders 152, 162 willpreferably operate under about 9 psig air pressure with a range of about7 psig to about 11 psig, whereas the bladder 24 will preferably operateunder about 3 psig air pressure with a range of about 2 psig to about 4psig.

[0076] As the pressure in the energy storage tank 37 drops below aminimum set point, as determined by a pressure transducer (not shown)that is part of the control 33, the control 33 activates the aircompressor 39 to re-fill the energy storage tank 37, increasing the airpressure in the energy storage tank 37 to a maximum pressure asdetermined by a second pressure transducer. The pressure range definedby the set points of the pressure transducers is called the operatingpressure envelope.

[0077] The pressure in the bladder 24 is monitored by a pressuretransducer and controlled by the control 33. The air pressure in thebladder 24 is ultimately applied on the fluid container 23. The pressurein the container 23 is applied to the tube 28. As fluid escapes from thefluid container 23, pressure in the bladder 24 decreases to a lowerpressure set point determined by a transducer. At that point, thecontrol 33 will activate a solenoid valve to allow compressed air toflow into the bladder 24 thus increasing the air pressure in the bladder24 until an upper pressure set point determined by the pressuretransducer is reached. Then the control 33 re-activates the solenoidvalve to shut-off and isolate the pressure between the energy storagetank 37 and the bladder 24.

[0078] The solenoid valves are, for example, available from PACKERCORPORATION, ______. The solenoid valves will preferably have anoperating voltage of about 1 volt to 12 volts DC, a power consumption ofabout 50 milliwatts to about 1000 milliwatts, and a response time ofabout 1 milliseconds to about 1000 milliseconds. The flow rate throughsolenoid valves is about 0.25 mL/minute (6.6×10⁻⁵ gallon/minute) toabout 1000 mL/minute (0.26 gallon/minute). The solenoid valve used tocontrol the pressure in the bladder has an operating voltage of 4 voltsDC and a power consumption of about 500 milliwatts.

[0079] A microprocessor 36, included in the control 33, includes aplurality of independent programs. The microprocessor 36 may alsoinclude a plurality of microprocessors. One program controls the bladder24, and the other program controls the occluder mechanism 40. It isknown that the more the bladder 24 is expanded, the less efficiently thebladder 24 transfers energy to the container 23. Therefore, the programcontained in the microprocessor is designed so that the pressure setpoint of the bladder 24 will be increased by a certain pressure at eachre-charge cycle. This pressure incrementation is called the bladderefficiency compensation pressure or the adjust pressure. Ideally, thepressure in the bladder 24 is as low as possible to prevent leaks orbursting of the container 23 and internal expansion of the tube 28, yetgreat enough to push liquid out of the container 23. The program alsoperiodically checks the pressure in the energy storage tank 37 and thepressure in the bladder 24.

[0080] The program used to operate the occluder mechanism 40 performsthree primary functions: user interface, operating pressure control, andoperating timing control. A Munich or other adjust pressure subroutineknown in the art is included in the program used to control the bladder24. As the bladder 24 becomes extended, determined by sensing cumulativecompressor 39 activity, a maximum pressure set point is biased upward.This method of cumulative pressure control reduces inefficiency ofenergy transfer through the bladder 24; therefore, the metering chamberis filled consistently and produces consistent bolus volumes leading tohigher flow rate accuracy.

[0081] As the fluid delivery device is switched on, by activating apower switch, the program that controls the bladder 24 executes a selftest. Upon successful completion of the self test, the program initiatespressurization of the bladder 24 and initiates a check on the pneumaticcomponents of the fluid delivery device for leaks and checks theposition of the occluders 152, 162 and the plunger 73. The leak testwill take approximately 30 seconds to complete; during this time ifliquid is allowed to escape from the container 23, the leak test willfail and an alarm may turn on. If no leak is found, the program willindicate a ready signal by emitting a low-high buzzer. Next, the programwill check for user input, preferably in the form of a password, fromthe user interface 38. From the time the power is switched on, theprogram will periodically activate the sequence described above if nopassword is received. If during this sequence the air pressure fallsbelow any of the set-points, the microprocessor will turn on the aircompressor 39. Additional programs may be used.

[0082] The user interface 38 includes three functions: a programmingpanel, an LCD display, and an IR communication port. The programmingpanel includes a keypad that is used to program, for example, the flowrates, bolus volumes, the number of doses, the volume to be infused, thetime of delivery, the status of the fluid delivery device, and/or thepressure to be applied to the upstream and downstream occluders 152,162. The keypad can may also be used to program a sequence of operationsfor the occluder mechanism 40. Each key press is acknowledged by a shortbeep. A volume to be infused may be selected from a list of bolusvolumes that includes, for example, 5 mL (0.00132 gallon), 10 mL(0.00264 gallon), 50 mL (0.0132 gallon), 100 mL (0.0264 gallon), 250 mL(0.066 gallon), 300 mL (0.079 gallon), and 999 mL (0.264 gallon).Preferably, flow rates may be selected from a list of flow rates thatincludes, for example, 0.5 mL/hr (0.000132 gallon/hr), 1 mL/hr (0.000264gallon/hr), 2 mL/hr (0.000528 gallon/hr), 3 mL/hr (0.000793 gallon/hr),4 mL/hr (0.00106 gallon/hr), 5 mL/hr (0.00132 gallon/hr), 10 mL/hr(0.00264 gallon/hr), 20 mL/hr (0.00528 gallon/hr), 50 mL/hr (0.0132gallon/hr), 100 mL/hr (0.0264 gallon/hr), and 200 mL/hr (0.0528gallon/hr). The status of the fluid delivery device is addressablethrough a switch that is used to start and/or stop the fluid deliverydevice. As the switch is activated, the microprocessor 36 will initiatethe infusion based on the programmed parameters received from the userinterface 38 and will be operated according to a time cycle enteredthrough the IR communications port. The switch is pushed again to stopthe fluid delivery. A menu switch can also be provided that allows apreview of the status of a fluid delivery.

[0083] The pressure to be applied to the upstream and downstreamoccluders 152, 162 is addressable through a load switch that manuallyactivates the venting of the solenoid valves 42, 44 of the plunger 73,respectively, and pressurizes both the solenoid valves 43, 45 thatcontrol the upstream and downstream occluders 152, 162, respectively.This feature is designed to provide easier loading of the tube 28 intothe occluder mechanism 40.

[0084] The LCD display provides a visual output of the programmedparameters of the fluid delivery. For example, when used as an infusionpump, the LCD displays bolus volume, flow rate, and status, and alsodisplays a current cumulate volume of liquid delivered to a patient. Thecurrent cumulative volume is determined based on the number of times abolus volume has been delivered to a patient.

[0085] The IR communications port examines and/or modifies the fluiddelivery device operating parameters, including the timing of thedelivery of a bolus volume, the bolus volume, and the operating pressureparameters. A program displays a menu of parameters along with thecurrent settings when the power of the fluid delivery device is switchedon or whenever a user requests such a display through the user interface38. The operating parameters are kept in an erasable programmable readonly memory (EPROM) and any changes made are persistent.

[0086] The occluder mechanism program also controls the air compressor39 that supplies the compressed air to the energy storage tank 37; thecompressed air from the energy storage tank 37 is used to operate theupstream and downstream occluders 152, 162 and the plunger 73. Apressure set-point and a pressure envelope can be adjusted through theIR communications port. The pressure in the energy storage tank 37 isnot critical to the performance of the occluder mechanism 40 so long asthe pressure remains above a minimum level that is definable based onthe operating pressure requirements of the components of the occludermechanism 40.

[0087] The occluder mechanism program also controls the timing of thesolenoid valves 42, 43, 44,45 and the timing of the delivery of theliquid. A solenoid valve timing control program is used to operate theupstream and downstream occluders 152, 162 and the plunger 73.

[0088] The scheduled timing control program is based on the selectedflow rate and the bolus size. When the flow rate and the bolus size areinput through the user interface 38, the program will automaticallycalculate the scheduled time for delivery. For example, to find the timeschedule for delivering at 100 mL/hr flow rate with the bolus size of0.083 mL, first the program assumes that the bolus size is consistentthroughout the delivery. To deliver 100 mL at 0.083 mL per bolus, willrequire 1204.8 delivery cycles; to operate the occluder mechanism 40 at1204.8 cycles per hour, or 3600 seconds, the occluder mechanism 40 willperform one cycle within 2.988 seconds. Accordingly, the delivery timeschedule can be calculated.

[0089] Referring to FIG. 15, a schematic of an arrangement utilizingthree solenoid valves with a single plunger, for use in the occludermechanism 40, is shown. The solenoid valve 43 is used to control theupstream occluder 152, the solenoid valve 45 is used to control thedownstream occluder 162, and the solenoid valve 42 is used to controlthe plunger 73.

[0090] Referring now to FIG. 16, an operating profile of the occludermechanism 40 utilizing the arrangement of FIG. 15 is presented. Thesolenoid valve 45 is energized, and common and normally closed ports areconnected allowing air pressure to enter the pneumatic cylinder of thedownstream occluder 162, thus pushing against the pre-loaded springforce to open the downstream occluder 162. This action allows the liquidto escape the metering chamber when the plunger 73 pushes on the tube28. The downstream occluder 162 remains opened (the solenoid valve 45remains energized) during the plunger 73 forward movement and until theplunger 73 reaches the maximum stroke during the time period (m). Afterthe time period (m), the solenoid valve 45 is de-energized and commonand normally opened ports are connected to vent the pneumatic cylinderof the downstream occluder 162. At this point, the pre-loaded springwill apply a force to pinch-off the tube 28 at the downstream occluder162.

[0091] After the downstream occluder 162 is opened for the time period(c), the solenoid valve 46 is energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of the plunger 73, thus pushing against the pre-loaded springforce to activate the plunger 73 forward for the time period (d). Thetime period (d−e) is designed to allow enough opened time for thesolenoid valve 42 so that sufficient pressure is built-up inside thepneumatic cylinder of the plunger 73. Then solenoid valve 42 isde-energized, venting the pneumatic cylinder of the plunger 73 to allowthe plunger 73 to return to its original position. Although the timefunctions are shown as step-functions, non-linear time functions arepossible.

[0092] After the solenoid 45 is de-energized for the time period (f),the solenoid 43 is energized, and common and normally closed ports areconnected allowing air pressure to enter the pneumatic cylinder of theupstream occluder 152, thus pushing against the pre-loaded spring forceto open the upstream occluder 152. This action allows the liquid toescape back to the fluid source through the upstream occluder 152, thusflushing back, which in turn will re-open a pinched-off area in the tube28 created by the upstream occluder 152.

[0093] After the flush-back cycle, while the upstream occluder 152 isstill open, both the solenoid valve 42 is de-energized. Common andnormally opened ports are connected allowing air to vent from thepneumatic cylinder of the plunger 73. At this point, the pre-loadedspring of the plunger 73 applies a force to push the plunger 73 open,thus relieving the tube 28 and creating a suction force to draw theliquid from the container 23 to fill the metering chamber.

[0094] After the time period (a/h), the solenoid 43 is de-energized, andcommon and normally opened ports are connected to vent the pneumaticcylinder of the upstream occluder 152. At this point, the pre-loadedspring of the upstream occluder 152 applies a force to pinch-off thetube 28 at the upstream occluder 152 and the control 33 switches intothe waiting mode for the remaining scheduled time before waking-up toperform the next delivery cycle. Once again, all of the above activitiesand sequences are operated within the scheduled time period (T) whichrepresents the frequency of delivery cycles at certain flow rates and agiven bolus volume.

[0095] Referring to FIG. 17, a schematic of an arrangement utilizingfour solenoid valves, for use in the occluder mechanism 40, is shown.The solenoid valve 43 is used to control the upstream occluder 152, thesolenoid valve 45 is used to control the downstream occluder 162, thesolenoid valve 42 is used to control the forward movement of the plunger73, and the solenoid valve 44 is used to vent the plunger 73.

[0096] Referring to FIG. 18, an operating profile of the occludermechanism 40 utilizing four solenoid valves is provided. As the solenoidvalve 45 is energized, common and normally closed ports are connectedallowing the air pressure to enter the pneumatic cylinder of thedownstream occluder 162, thus pushing against the pre-load spring forceto open the downstream occluder 162. This allows fluid to escape thetube 28 when the plunger 73 pushes on the tube 28. The downstreamoccluder 162 remains opened as the plunger 73 moves to compress the tube28 for the time period (c+d+e).

[0097] After the downstream occluder 162 is opened, the solenoid valve42 is energized, common and normally closed ports are connected allowingthe air pressure to enter the pneumatic cylinder of the plunger 73 thuspushing against the pre-load spring force to activate the plungerforward for the time period (d). The time period (d−e) is designed toallow enough open time for the solenoid valve 42 such that sufficientair pressure is built-up inside the pneumatic cylinder of the plunger73. Then the solenoid 44 is de-energized. At this point, the plunger 73reaches the end of its stroke and remains in this forward position.

[0098] After the solenoid valve 42 is de-energized for the time period(e), the solenoid valve 45 is de-energized, common and normally openedports are connected to vent the pneumatic cylinder associated with thedownstream occluder 162. At this point, the pre-load spring of thedownstream occluder 162 will apply a force to pinch-off the tube 28 atthe downstream occluder 162. The time period (e) is designed as avariable to define the amount of time the downstream occluder 162 is inthe open position; this variable can be eliminated if a value for thetime the downstream occluder 162 is in the open position is established.

[0099] After the solenoid valve 45 is de-energized for the time period(f), the solenoid valve 43 is energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of the upstream occluder 152, thus pushing against the pre-loadspring force to open the upstream occluder 152. This action allowsliquid to fill the metering chamber when the plunger 73 returns to anopen position. The upstream occluder 152 remains opened for the a timeperiod to ensure that fluid completely fills the metering chamber. Thetime period (f) is designed to ensure that the downstream occluder 162is closed prior to opening of the upstream occluder 152.

[0100] The solenoid valve 44 is also energized at the same time that thesolenoid valve 43 is energized, and common and normally closed ports areconnected allowing air to vent from the pneumatic cylinder of theplunger 73. At this point, the pre-load spring of the plunger 73 willpush the plunger 73 back to an open position, relieving the tube 28 andcreating a suction force to draw liquid from the container 23 to fillthe metering chamber. The upstream occluder 152 remains opened for the atime period to ensure that fluid completely fills the metering chamber.

[0101] In the embodiment of the fluid delivery device depicted in FIGS.17 and 18, a fluid flush-back operation is possible. In the fluidflush-back operation, fluid is pushed through the tube 28 back towardsthe source of the fluid. In this way, the force of the flush-back can beused to re-open an otherwise collapsed tube 28. The flush-back isfunctional so long as there is some fluid in the tube 28.

[0102] Referring now to FIG. 19, a schematic of an alternativeembodiment of a fluid delivery mechanism made in accordance with theprinciples of the present invention is seen in which a duel plungerarrangement is utilized. Consistent with the description of the relatedembodiment depicted in FIGS. 5 through 18, where possible like numbersare used to identify like elements. When the tube 28 is loaded in thefluid delivery device, a segment of the tube 28 is pre-compressedbetween a first fixed plate 75 and a first plunger 72 while a furthersegment of the tube 28 is pre-compressed between a second fixed plate 76and a second plunger 73. The first fixed plate 75 and the second fixedplate 76 may be portions of one continuous plate. Two occluders 152, 162are provided with one on each side of the plungers 72, 73 to pinch-offthe tube 28. A metering chamber is disposed between the two occluders152, 162.

[0103]FIGS. 20 through 25 depict the alternative embodiment of theoccluder mechanism 40 of FIG. 19. FIG. 20 is a plan sectional view ofthe occluder mechanism 40. FIG. 21 is an elevation sectional view of theoccluder mechanism 40.

[0104] The upstream occluder 152 and the downstream occluder 162 areboth spring loaded to a closed position. The plungers 72, 73 are bothspring loaded to an open position. The occluders 152, 162 and theplungers 72, 73 are each connected to pneumatic cylinders, which areoperated by compressed air. Each pneumatic cylinder associated withoccluders 152, 162 is preferably controlled by a 3-way solenoid valve43, 45, and the two pneumatic cylinders associated with the plungers 72,73 are preferably controlled by solenoid valves 42, 44, respectively. Acontrol 33, that includes a microprocessor 36, controls the operation ofthe solenoid valves 42, 43, 44, 45. The microprocessor 36 may include aplurality of microprocessors. The function and operation of the control33 and the microprocessor 36 in the present embodiment is similar to thefunction and operation of these components as described above.

[0105] Optionally, a pressure transducer (not shown) may be used tofacilitate controlling a stroke distance of the plungers 72, 73.Associated with the pressure transducer an additional solenoid valve(not shown) is provided for each of the plungers 72, 73. The additionalsolenoid provide the capability of opening and closing the venting ofair from the pneumatic cylinders. The pressure transducer provides anoutput signal proportional to the pressure in each of the pneumaticcylinders. The output signal is sensed by control 33. The control 33controls the opening and the closing of the solenoid valves 42, 44 andthe additional solenoid valves associated with each plunger. Thus, thesolenoid valves 42, 44 and the additional solenoid valves can be openedand closed to incrementally pressure or vent the pneumatic cylinders andthereby control the stroke of the plungers 72, 73.

[0106] To ensure the tube 28 is opened and ready for delivery, thedownstream occluder 162 is open prior to the plungers 72, 73 movingtoward a closed position. To prevent back flow, the downstream occluder162 also is closed before the plungers 72, 73 return to an openposition. The upstream occluder 152 is not opened during the downstreamoccluder open period. This method of operating sequences is designed toprevent free-flow of the liquid.

[0107] The upstream and downstream occluders 152, 162 are mechanicalvalves as described above. The design, manufacture and function providedby the occluders 152, 162 in the present embodiment is consistent withthe description above. The plungers 72, 73 are designed as moving platesto apply pressure on the tube 28 as described above. Accordingly, thedesign, manufacture and function provided by the plungers 72, 73 in thepresent embodiment is consistent with the description above.

[0108] The occluder mechanism 40 is constructed with four pneumaticcylinders incorporated for the operation of the upstream and downstreamoccluders 152, 162 and the plungers 72, 73. Each of the pneumaticcylinders associated with the upstream and downstream occluders 152, 162are connected directly to an in-line solenoid valve. The plungers 72, 73are each connected to at least one in-line solenoid valve.

[0109]FIG. 22 presents an elevation sectional view of the occludermechanism 40 taken along axis A-A of FIG. 20. The upstream occluder 152is shown in a closed position and the plunger 72 is likewise shown in aclosed position. The downstream occluder 162 and the plunger 73 are bothshown in an opened position. The position of the solenoid valve 42,operatively associated with the plunger 72 is shown. Similarly theposition of the solenoid valve 44, operatively associated with theplunger 73 is shown.

[0110]FIG. 23 is an elevation sectional view taken along the B-B axis ofFIG. 20. The inlet pneumatic connection 47 between the solenoid valve 42and the plunger 72 is illustrated. Similarly, the inlet pneumaticconnection 49 between the solenoid valve 44 and the plunger 73 isillustrated.

[0111]FIG. 24 is an elevation sectional view taken along the C-C axis ofFIG. 20. The location of the pneumatic connection from the solenoidvalve 43, and from the solenoid valve 45, to the upstream occluder 152and the downstream occluder 162, respectively, can be seen.

[0112]FIG. 25 is an elevation sectional view taken along the D-D axis ofFIG. 20. The outlet pneumatic connection 82 between the solenoid valve42 and the plunger 72 is illustrated. Similarly, the outlet pneumaticconnection 84 between the solenoid valve 44 and the plunger 73 isillustrated. The outlets 82, 84 vent the pneumatic cylinders associatedwith each of the plungers 72, 73, respectively.

[0113] The cross-sectional views of the downstream and upstreamoccluders 152, 162 are similar to views presented in FIGS. 12 and 13,respectively. Thus the view along section E-E of FIG. 20 has the sameappearance as shown in FIG. 12. Likewise, the view along section F-F ofFIG. 20 has the same appearance as shown in FIG. 13.

[0114] Referring to FIG. 26, a schematic of a dual plunger arrangementutilizing four solenoid valves, for use in the occluder mechanism, isshown. The solenoid valve 43 is used to control the upstream occluder152, the solenoid valve 45 is used to control the downstream occluder162, the solenoid valve 42 is used to control the plunger 72, and thesolenoid valve 44 is used to control the plunger 73. The dual plungerarrangement provides the following functions: at higher liquid flowrates, both plungers 72, 73 may be programmed to operate in parallel toproduce larger bolus volumes; at medium liquid flow rates, one of theplungers, plunger 72 for example, may be operated while plunger 73 isdisabled to produce more stable flow, or both plungers 72, 73 can beprogrammed to operate in series to save energy; and at slower flow rateswhere the upstream occluder 152 is pinching-off the tube 28 for a longperiod of time, the plungers 72, 73 may be programmed to perform aflush-back operation. When the tubing 28 is pinched-off by the occluders152, 162 for a long period of time, the tube 28 may not re-open to allowa fluid to refill the metering chamber. The flush-back operation pushesliquid back into the tube 28 towards the container 23 and thus opens thetube 28 at the opened upstream occluder 152. In the preferredembodiment, the flush-back operation is provided by utilizing at leasttwo plungers. The use of two plungers assures there being some fluid inthe tube 28 to provide the flush-back.

[0115] Generally, the flush-back operation is the process by which thetube 28 is restored or re-expanded to about its original diameter sothat an accurate bolus volume will be infused to a patient. When thetube 28 is pinched-off for a long period of time by the downstreamoccluder 152, the tube 28 will only slowly uncompress once thedownstream occluder 152 moves to its open position. Subsequently, themetering chamber may not completely fill prior to the downstreamoccluder 152 closing in anticipation of infusing a patient with a bolusvolume. A consequence of the incompletely filled metering chamber, isthat a patient will be infused with an inaccurate bolus volume. Bypushing the liquid in a flow direction that is back towards the sourceof the liquid through the tube 28, where the tube 28 was pinched-off,the tube may be re-expanded to about its original diameter before themetering chamber is refilled with the liquid. This is described in moredetail below.

[0116] At high liquid flow rates, the solenoid valve 45 is energized,and common and normally closed ports are connected allowing air pressureto enter the pneumatic cylinder of the downstream occluder 162 thuspushing against the pre-loaded spring force to open the downstreamoccluder 162. This action allows the liquid to escape the meteringchamber when either the plunger 72 or the plunger 73 pushes on the tube28.

[0117] Referring now to figure 27, the downstream occluder 162 remainsopened (the solenoid valve 45 remains energized) during the plungers 72,73 forward movement and until the plungers 72, 73 reach the maximumstroke during the time period (m). After this time period (m), thesolenoid valve 45 is de-energized and common and normally opened portsare connected to vent the pneumatic cylinder of the downstream occluder162. At this point, the pre-loaded spring will apply its force topinch-off the tube 28 at the downstream occluder 162.

[0118] After the downstream occluder 162 is opened for a time period(c), the solenoid valve 42 is energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of plunger 72, thus pushing against the pre-loaded spring forceto activate the plunger 72 forward for a time period (d). This timeperiod (d−e) allows enough opened time for the solenoid valve 42 so thatsufficient pressure is built-up inside the pneumatic cylinder of theplunger 72 to deliver the first bolus. Then, after the downstreamoccluder 162 is opened for a time period (n), the solenoid 44 isenergized, and common and normally closed ports are connected allowingair pressure to enter the pneumatic cylinder of the plunger 73, thuspushing against the pre-loaded spring force to activate the plunger 73forward for a time period (o). This time period (o-e) allows sufficientopened time the solenoid valve 44 so that sufficient pressure isbuilt-up inside the pneumatic cylinder of the plunger 73 in order todeliver the second bolus. Although the time functions are shown as stepfunctions, non-linear functions are possible.

[0119] After the solenoid valve 45 is de-energized for a time period(f), the solenoid valve 43 is energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of the upstream occluder 152, thus pushing against thepre-loaded spring force to open the upstream occluder 152. This actionallows the liquid to fill the metering chamber when the plungers 72, 73return. The upstream occluder 152 is opened for a time period (a/h) toensure that the liquid completely fills the metering chamber. The timeperiod (f) is designed to ensure that the downstream occluder 162 isclosed prior to opening the upstream occluder 152.

[0120] At the same time that the solenoid valve 43 is energized, thesolenoid valves 42 and 44 are also de-energized, and common and normallyopened ports are connected allowing air to vent from the pneumaticcylinders of the plungers 72, 73. At this point, the pre-loaded springswill apply a force each to push the plungers 72, 73 back, thus relievingthe tube 28 and creating a suction force to draw the liquid from thecontainer 23 to fill the metering chamber. The upstream occluder 152remains opened for the time period (a/h) to ensure that the liquidcompletely fills the metering chamber.

[0121] After the time period (a/h), the solenoid valve 43 isde-energized, and common and normally opened ports are connected to ventthe pneumatic cylinder of the upstream occluder 152. At this point, thepre-loaded spring of the upstream occluder 152 applies a force topinch-off the tube 28 at the upstream occluder 28. The control 33switches into the waiting mode for the remaining scheduled time beforewaking-up to perform the next delivery cycle.

[0122] All of the above activities and sequences are operated within thescheduled time period (T). The scheduled time period (T) represents thefrequency of delivery cycle at certain flow rates and a given bolusvolume.

[0123] Referring now to FIG. 28, in the medium flow rate range ofdelivery, the operating profile is similar to the higher flow rates withthe exception that the plunger 73 is disabled or is programmed toactivate in series with the plunger 72. If the plunger 73 is programmedto operate, the time periods (m), (d), (f), and (T) are extended toaccept the second bolus within a single delivery cycle.

[0124] In the lower flow rate range of delivery, the scheduled timebetween delivery cycles is long, causing the tube 28 to be pinched-offand deformed at the upstream occluder 152 as described above. Thepinched-off tube 28 can prevent the liquid from filling the meteringchamber quickly.

[0125] Referring now to FIG. 29, to deal with the lower flow rate rangeof delivery, the solenoid valve 45 is energized, and common and normallyclosed ports are connected allowing air pressure to enter the pneumaticcylinder of the downstream occluder 162, thus pushing against thepre-loaded spring force to open the downstream occluder 162. This actionallows the liquid to escape the metering chamber when the plunger 72and/or the plunger 73 pushes on the tube 28. The downstream occluder 162remains opened (the solenoid valve 45 remains energized) during theplungers 72, 73 forward movement and until the plungers 72, 73 reach themaximum stroke during the time period (m). After the time period (m),the solenoid valve 45 is de-energized and common and normally openedports are connected to vent the pneumatic cylinder of the downstreamoccluder 162. At this point, the pre-loaded spring will apply a force topinch-off the tube 28 at the downstream occluder 162.

[0126] After the downstream occluder 162 is opened for the time period(c), the solenoid valve 42 is energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of the plunger 72, thus pushing against the pre-loaded springforce to activate the plunger 72 forward for the time period (d). Theplunger 72 remains at its forward position until the flush-back cycle iscompleted. The time period (d−e) is designed to allow enough opened timefor the solenoid valve 42 so that sufficient pressure is built-up insidethe pneumatic cylinder of the plunger 72. Then solenoid valve 42 isde-energized, venting the pneumatic cylinder of the plunger 72 to allowthe plunger 72 to return to its original position.

[0127] After the solenoid 45 is de-energized for the time period (f),the solenoid 43 is energized, and common and normally closed ports areconnected allowing air pressure to enter the pneumatic cylinder of theupstream occluder 152, thus pushing against the pre-loaded spring forceto open the upstream occluder 152. This action allows the liquid toescape back to the fluid source through the upstream occluder 152, thusflushing back, which in turn will re-open a pinched-off area in the tube28 created by the upstream occiuder 152.

[0128] At the same time that the solenoid valve 43 is energized, thesolenoid valve 44 is also energized, and common and normally closedports are connected allowing air pressure to enter the pneumaticcylinder of the plunger 73, thus pushing against the pre-loaded springforce to activate the plunger 73 forward for the time period (o). Thetime period (o) allows enough opened time for solenoid valve 44 so thatsufficient pressure is built-up in the pneumatic cylinder of the plunger73, in order to perform the reverse delivery. Then solenoid 44 isde-energized, venting the pneumatic cylinder of the plunger 73 to allowthe plunger 73 to return to its original position. As the plunger 73moves forward, a certain volume of the liquid is pushed back to spikethe upstream occluder 152 opened. This is called the flush-back cycle.

[0129] After the flush-back cycle, while the upstream occluder 152 isstill open, both the solenoid valves 42 and 44 are de-energized. Commonand normally opened ports are connected allowing air to vent from thepneumatic cylinder of the plungers 72, 73. At this point, the pre-loadedsprings of the plungers 72, 73 apply a force each to push the plungers72, 73 open, thus relieving the tube 28 and creating a suction force todraw the liquid from the container 23 to fill the metering chamber.

[0130] After the time period (a/h), the solenoid 43 is de-energized, andcommon and normally opened ports are connected to vent the pneumaticcylinder of the upstream occluder 152. At this point, the pre-loadedspring of the upstream occluder 152 applies a force to pinch-off thetube 28 at the upstream occluder 152 and the control 33 switches intothe waiting mode for the remaining scheduled time before waking-up toperform the next delivery cycle. Once again, all of the above activitiesand sequences are operated within the scheduled time period (T) whichrepresents the frequency of delivery cycles at certain flow rates and agiven bolus volume.

[0131] It is important to control the operating phases and theassociated timing in order to achieve the flow accuracy of the presentinvention. There are three different dynamic phases within the operationof the occluder mechanism 40. These are the filling phase, the deliveryphase, and the delay or waiting phase.

[0132] The filling phase starts from the time the solenoid valve 43 isenergized to open the upstream occluder 152; the plungers 72, 73 returnto create a suction force generated by the elasticity of the tube 28 andthe pressured container 23 to draw the liquid into the metering chamber.The filling phase ends when the upstream occluder 152 closes to shut-offthe tube 28, separating the metering chamber from the container 23.

[0133] The delivery phase starts from the time the solenoid valve 45 isenergized to open the downstream occluder 162; the plungers 72, 73 movesforward, pushing on the tube 28 to deliver the bolus. The solenoid valve45 is de-energized (or re-energized) to close the downstream occluder162, followed by a delay period. This delay period is used to ensurethat the downstream occluder 162 is completely shut-off prior to theopening of the upstream occluder 152.

[0134] The last phase of a delivery cycle is the delay or waiting phase.Preferably, the waiting phase is the time period left-over from thescheduled time (T_(s)) after the delivery and filling phases. Thefollowing formula describes the waiting phase:

T _(w) =T _(s)−(T _(f) +T _(d))

[0135] Where, T_(w) is the time of the waiting phase, T_(s) is thescheduled time, T_(f) is the time of the filling phase, and T_(d) is thetime of the delivery phase. Since the scheduled time varies based on theflow rates, the waiting time is also based on the flow rates. The bolussizes will also be affected depending on which phase sequentially startsthe delivery cycle, and the method of refilling the metering chamber.

[0136] The pneumatic-actuated fluid delivery mechanisms of the presentinvention may be operated as modular systems using a single compressor,such as an air compressor, to provide compressed fluid to a plunger andan occluder and, optionally, to an energy storage tank. An optionalinflatable bladder may be included with each individual fluid deliverymechanism used in the modular system. Thus a plurality of medicalliquids, for example, could be delivered to a patient using such amodular system.

[0137] An option to using an air compressor to operate the components ofthe occluder mechanism 40 is a cam-actuated mechanism depicted in FIG.30. An electric motor 181 rotatably drives a cam shaft 189 causing anincremental rotation of cams disposed on the cam shaft 189. Operativelyassociated with the cams are cam followers. The rotation of the camshaft 189 thus causes the rotation of the cams which in turn act uponthe cam followers in a manner that is known in the art. The camfollowers in turn operate the components of the occluder mechanism 40.

[0138] A cam 172 and an associated cam follower 182 illustrate theoperation of the cam-actuated mechanism 180. As the cam 172 is rotated,the cam follower 182 is caused to move in plane and into and away fromthe cam shaft 189. The cam follower 182 is further operativelyassociated with the downstream occluder 162 such that as the camfollower moves into and away from the cam shaft 189, the downstreamoccluder is caused to open and close. As illustrated, the downstreamoccluder 162 is integrally formed at the distal end of the cam follower172. In a similar manner, a cam follower 183 is operatively associatedwith the upstream occluder 152 and the upstream occluder 152 is causedto open by the rotation of the cam 173.

[0139] It is possible to have a plurality of cams operatively associatedwith a plurality of plungers. As illustrated in FIG. 30, five camfollowers 185 a, 185 b, 185 c, 185 d, 185 e are operatively associatedwith five different cams 175 a, 175 b, 175 c, 175 d, 175 e. At thedistal end of each of the cam followers 185 a, 185 b, 185 c, 185 d, 185e are disposed five plungers, respectively. The plungers are caused toopen and close by the rotation of the cams 175 a, 175 b, 175 c, 175 d,175 e acting on the cam followers 185 a, 185 b, 185 c, 185 d, 185 e,respectively.

[0140]FIG. 30 also illustrates one embodiment for placing the tube 28(not shown) in position to be acted on by the occluder mechanism 40. Acover 195, for example, may have a trough 193 disposed on a face of thecover 195. The cover 195 may be hingedly attached to the occludermechanism 40. When the cover 195 is rotated towards the plungers 175 a,175 b, 175 c, 175 d, 175 e and the occluders 152, 162, the tube 28 maybe brought into position to be acted on by plungers 175 a, 175 b, 175 c,175 d, 175 e and the occluders 152, 162.

[0141] Referring to FIG. 31, the cam 175 a is seen in a cross-sectionalview disposed on the cam shaft 189. The cam follower 185 ais operativelyassociated with the cam 175 a. Typical of cams, the cam 175 a defines achange in its surface elevation. This is seen as an upper region 211 anda lower region 213.

[0142] As the cam 175 a rotates on the cam shaft 189, the cam follower185 ais moved back away from the cam shaft 189 when the cam follower 175a is in contact with upper region 211. When the cam follower 175 abegins to move into the lower region 211, the cam follower 175 a movescloser to the cam shaft 189. The longitudinal axis of the cam followeris about coextensive with the transverse axis of the cam shaft 189.

[0143] The cams of the cam-actuated mechanism 180 are arranged about thecam shaft 189 so that as the electric motor rotates the cam shaft 189the cam followers operate the components of the occluder mechanism 40 inthe proper sequence. The proper sequence is controlled by the controller33 and the program included in the microprocessor 36, as describedabove. Thus, it can be seen that the cam-actuated mechanism 180 of thepresent invention can operate the plungers 175 a, 175 b, 175 c, 175 d,175 e and the upstream and downstream occluders 152, 162. In doing so,the cam-actuated mechanism replaces the solenoid valves 42, 43, 44 and45 and results in the elimination of the pneumatic cylinders operativelyassociated with each of the plungers 175 a, 175 b, 175 c, 175 d, 175 eand the upstream and downstream occluders 152, 162, respectively.

[0144]FIGS. 32a and 32 b illustrates an operating profile diagram forthe occluder mechanism 40 of FIG. 30. Both the FIGS. 32a and 32 b areidentical with respect to an identification of an open and a closedposition for the cams 172, 175 a, 175 b, 175 c, 175 d, 175 e, and 173.FIG. 32a describes the positions while FIG. 32b identifies the anglethrough which the cam shaft 189 will rotate to effect the positionsdescribed in FIG. 32a. With the cam actuated mechanism it is possible toperform the flush-back operation using only one plunger. Where aplurality of plungers are used, flush-back may be effected bysimultaneously activating all of the plungers. The flush-back process isillustrated in FIG. 32a.

[0145] It should be understood that various changes and modifications tothe preferred embodiments described herein will be apparent to thoseskilled in the art. Such changes and modifications can be made withoutdeparting from the spirit and scope of the present invention and withoutdiminishing its attendant advantages. It is therefore intended that suchchanges and modifications be covered by the appended claims.

We claim:
 1. A device for providing a flow of a deliverable fluidthrough a tube, the device comprising: a metering chamber in the tubeformed between a pair of occluders; a first occluder located upstream ofthe metering chamber; a second occluder located downstream of themetering chamber; each occluder having an open position and a closedposition for releasably closing off the metering chamber; and a firstplunger and a second plunger, each plunger having an open position and aclosed position for releasably compressing the metering chamber.
 2. Thedevice of claim 1 further including means for providing the deliverablefluid to the metering chamber under pressure.
 3. The device of claim 1further wherein the means for providing the source of the deliverablefluid under pressure includes an inflatable bladder.
 4. The device ofclaim 3 further wherein the means for providing the source of thedeliverable fluid under pressure includes a fluid compressor forproviding compressed fluid to the inflatable bladder.
 5. The device ofclaim 2 further wherein the means for providing the source of thedeliverable fluid under pressure includes an energy storage tank influid communication with a fluid compressor and the inflatable bladder,the energy storage tank storing the compressed fluid under a pressure.6. The device of claim 5 wherein the fluid compressor intermittentlyprovides compressed fluid to the energy storage tank.
 7. The device ofclaim 5 further wherein the pressure in the energy storage tank isincreased over time.
 8. The device of claim 5 further including apressure transducer in fluid communication with the energy storage tankand in electrical communication with the fluid compressor such that whena high pressure occurs the fluid compressor is switched off.
 9. Thedevice of claim 5 wherein the fluid compressor provides pressure to theenergy storage tank and further wherein a second fluid compressorprovides pressure to the inflatable bladder.
 10. The device of claim 1further including a closed pressure system defined upstream of themetering chamber.
 11. The device of claim 10 further wherein the closedpressure system is a negative pressure.
 12. The device of claim 1wherein the occluder is fluid actuated.
 13. The device of claim 12wherein the fluid-actuated occluder includes a solenoid.
 14. The deviceof claim 1 wherein the occluder is biased to a closed position.
 15. Thedevice of claim 1 wherein the first plunger is fluid actuated.
 16. Thedevice of claim 15 wherein the first fluid-actuated plunger includes apneumatic cylinder.
 17. The device of claim 15 wherein the first plungeris biased in an open position.
 18. The device of claim 1 furtherincluding means for opening and closing the occluder and the first andsecond plungers.
 19. The device of claim 18 wherein the means foropening and closing the occluder and the plunger includes a cam-actuatedmechanism.
 20. A device for providing a flow of a liquid through a tube,the device comprising: a first means for occluding the tube at a firstlocation; a second means for occluding the tube at a second location; afirst means between the first location and the second location forcompressing the liquid in the tube; and a second means between the firstlocation and the second location for compressing the liquid in the tube.21. The device of claim 20 further including means for providing to thetube a source of liquid under pressure.
 22. The device of claim 21further wherein the means for providing a source of liquid underpressure includes a fluid compressor for providing compressed fluid toan inflatable bladder.
 23. The device of claim 21 further wherein themeans for providing a source of liquid under pressure includes an energystorage tank in fluid communication with a fluid compressor and theinflatable bladder, the energy storage tank storing the compressed airunder a pressure.
 24. The device of claim 23 wherein the fluidcompressor intermittently provides compressed fluid to the energystorage tank.
 25. The device of claim 23 further wherein the pressure inthe energy storage tank is increased over time.
 26. The device of claim23 further including a pressure transducer in fluid communication withthe energy storage tank and in electrical communication with the fluidcompressor such that when high pressure occurs the fluid compressor isswitched off.
 27. The device of claim 23 wherein the fluid compressorprovides pressure to the energy storage tank and further wherein asecond fluid compressor provides pressure to the inflatable bladder. 28.The device of claim 20 further including a closed pressure systemdefined upstream of a metering chamber, the metering chamber disposedbetween the first occluding means and the second occluding means. 29.The device of claim 28 further wherein the closed pressure system is anegative pressure.
 30. The device of claim 20 wherein the means foroccluding the tube includes an occluder.
 31. The device of claim 30wherein the occluder is fluid actuated.
 32. The device of claim 31wherein the fluid-actuated occluder includes a solenoid.
 33. The deviceof claim 30 wherein the occluder is biased to a closed position.
 34. Thedevice of claim 30 wherein the occluder is cam actuated.
 35. The deviceof claim 20 wherein the means for compressing the tube includes aplunger.
 36. The device of claim 35 wherein the plunger is fluidactuated.
 37. The device of claim 36 wherein the fluid-actuated plungerincludes a pneumatic cylinder.
 38. The device of claim 35 wherein theplunger is biased in an open position.
 39. The device of claim 35wherein the plunger is cam actuated.
 40. A method for delivering aliquid, the method comprising: providing a source of liquid in fluidcommunication with a metering chamber; releasably pinching-off thechamber near the source of the liquid at a first location; releasablypinching-off the chamber at a second location that is downstream fromthe source of the liquid and the first location; releasing the firstlocation; and compressing the chamber between the first location and thesecond location, thereby generating a flow of the liquid through thetube.
 41. The method of claim 40 wherein the step of providing a sourceof liquid in fluid communication with the chamber further includesproviding the liquid under pressure.
 42. The method of claim 40 whereinthe step of providing a source of liquid in fluid communication with thechamber further includes providing a closed pressure system definedupstream of the chamber.
 43. The method of claim 42 further wherein stepof providing a closed pressure system further includes providing anegative pressure.
 44. The method of claim 40 wherein the step ofreleasably pinching-off the chamber further utilizes fluid actuation.45. The method of claim 40 wherein the step of compressing the chamberfurther utilizes fluid actuation.
 46. A device for use with a tube and acontainer containing a liquid in fluid communication with the tube, thedevice comprising: a metering chamber in the tube; a bladder forcompressing the container thereby pressurizing the liquid in the tubeand causing the liquid to flow into the metering chamber; and a plungerfor releasably compressing the metering chamber and thereby generating aflow of the liquid from the metering chamber.
 47. The device of claim 46further including an energy storage tank in fluid communication with thebladder and in fluid communication with a fluid compressor for storingcompressed fluid under pressure.
 48. The device of claim 47 wherein thefluid compressor intermittently provides compressed fluid to the energystorage tank.
 49. The device of claim 48 further wherein the pressure inthe bladder is increased over time.
 50. The device of claim 47 furtherincludes a pressure transducer in fluid communication with the energystorage tank and in electrical communication with the fluid compressorsuch that when high pressure occurs the fluid compressor is switchedoff.
 51. The device of claim 47 wherein the fluid compressor providespressure to the energy storage tank and further wherein a second fluidcompressor provides pressure to the occluder.
 52. The device of claim 46further wherein the metering chamber is defined by two occluders havingan open position and a closed position for releasably pinching-off thetube.
 53. The device of claim 52 wherein the occluders are biased to aclosed position.
 54. The device of claim 52 wherein the occluders arefluid-actuated.
 55. The device of claim 54 wherein the fluid-actuatedoccluders includes a solenoid.
 56. The device of claim 52 wherein theoccluder is cam actuated.
 57. The device of claim 46 wherein the plungeris fluid actuated.
 58. The device of claim 57 wherein the fluid-actuatedplunger includes a pneumatic cylinder.
 59. The device of claim 46wherein the plunger is biased in an open position.
 60. The device ofclaim 46 wherein the plunger is cam actuated.
 61. A device for providinga flow of a liquid through a tube, the device comprising: means forproviding a source of liquid under pressure and in fluid communicationwith the tube; a first means for occluding the tube at first location; asecond means for occluding the tube at a second location; and means forcompressing tube between the first occluding location and the secondoccluding location.
 62. The device of claim 61 further wherein the meansfor providing a source of liquid under pressure includes an inflatablebladder.
 63. The device of claim 62 further wherein the means forproviding a source of liquid under pressure includes a fluid compressorfor providing compressed fluid to the inflatable bladder.
 64. The deviceof claim 62 further wherein the means for providing a source of liquidunder pressure includes an energy storage tank in fluid communicationwith a fluid compressor and the inflatable bladder, the energy storagetank storing the compressed air under a pressure.
 65. The device ofclaim 64 wherein the fluid compressor intermittently provides compressedfluid to the energy storage tank.
 66. The device of claim 64 furtherwherein the pressure in the energy storage tank is increased over time.67. The device of claim 64 further includes a pressure transducer influid communication with the energy storage tank and in electricalcommunication with the fluid compressor such that when high pressureoccurs the fluid compressor is switched off.
 68. The device of claim 64wherein the fluid compressor provides pressure to the energy storagetank and further wherein a second fluid compressor provides pressure tothe occluder.
 69. The device of claim 61 wherein the device isambulatory.
 70. The device of claim 61 wherein the means for occludingthe tube includes an occluder.
 71. The device of claim 70 wherein theoccluder is fluid actuated.
 72. The device of claim
 71. wherein thefluid-actuated occluders includes a solenoid.
 73. The device of claim 70wherein the occluders are biased to a closed position.
 74. The device ofclaim 70 wherein the occluder is cam actuated.
 75. The device of claim61 wherein the means for compressing the tube includes a plunger. 76.The device of claim 75 wherein the plunger is fluid actuated.
 77. Thedevice of claim 76 wherein plunger includes a pneumatic cylinder. 78.The device of claim 75 wherein the plunger is biased in an openposition.
 79. The device of claim 75 wherein the plunger is camactuated.
 80. A method for infusing liquid, the method comprising:providing a source of liquid under pressure in fluid communication witha tube; compressing the tube between the first location and the secondlocation; pinching-off the tube distal to the source of the liquid at afirst location; releasing the tube between the first location and thesecond location; pinching-off the tube at a second location that isproximal to the source of the liquid and the first location; andcompressing the tube between the first location and the second location.81. The method of claim 80 wherein the step of releasably pinching-offthe tube further utilizes fluid actuation.
 82. The method of claim 80wherein the step of compressing the tube further utilizes fluidactuation.
 83. A method of pumping fluid comprising: providing a closedpressure fluid system including a source of fluid and a tube; closingthe tube in a first location to isolate the closed pressure system;compressing the tube downstream of the closed tube; closing the tube ina second location downstream of the compressed tube to maintain theisolation of the closed pressure system; and opening the tube in thefirst location.
 84. The method of claim 83 wherein the closed pressuresystem is a negative pressure system.
 85. The method of claim 83 whereinthe closed pressure system is a positive pressure system.
 86. The methodof claim 83 wherein the step of providing a positive pressure fluidsystem further includes providing the fluid under pressure.
 87. Themethod of claim 83 wherein the step of closing the tube in a firstlocation further includes utilizing fluid actuation.
 88. The method ofclaim 83 wherein the step of compressing the tube further includesutilizing fluid actuation.
 89. A device comprising: at least one fluidcompressor for providing compressed fluid; an energy storage tank influid communication with the fluid compressor for storing the compressedfluid under a pressure; and a fluid driven mechanism in fluidcommunication with the energy storage tank, the energy storage tankproviding pressurized fluid to operate said fluid driven mechanism tomove liquid through a tube operatively associated with the fluid drivenmechanism.
 90. The device of claim 89 wherein the fluid compressorintermittently provides compressed fluid to the energy storage tank. 91.The device of claim 89 further includes a pressure transducer in fluidcommunication with the energy storage tank and in electricalcommunication with the fluid compressor such that when a high pressureoccurs the fluid compressor is switched off.
 92. The device of claim 89wherein the fluid compressor provides pressure to the energy storagetank and further wherein a second fluid compressor provides pressure toan inflatable bladder which presses on a container of liquid connectedto the tube operatively associated with the fluid driven mechanism tocreate a source of pressurized liquid for the fluid driven mechanism.93. The device of claim 89 wherein the device is a medical pump.
 94. Thedevice of claim 93 wherein the pump is ambulatory.
 95. The device ofclaim 89 further wherein the fluid driven mechanism includes twooccluders having an open position and a closed position for releasablypinching-off the tube.
 96. The device of claim 95 wherein the occludersare biased to a closed position.
 97. The device of claim 95 wherein theoccluders are fluid actuated.
 98. The device of claim 97 wherein thefluid-actuated occluders includes a solenoid.
 99. The device of claim 95wherein the occluders are cam actuated.
 100. The device of claim 89further wherein the fluid driven mechanism includes a plunger forreleasably compressing a chamber.
 101. The device of claim 100 whereinthe plunger is fluid actuated.
 102. The device of claim 101 wherein thefluid-actuated plunger includes a pneumatic cylinder.
 103. The device ofclaim 100 wherein the plunger is biased in an open position.
 104. Thedevice of claim 100 wherein the plunger is cam actuated.
 105. The deviceof claim 89 wherein the fluid driven mechanism includes a plurality offluid driven mechanisms.
 106. A device for providing a flow of a liquidthrough a tube, the device comprising: a fluid-actuated chamber forplacing a source of liquid under pressure connected to the tube; atleast two fluid-actuated occluders having an open position and a closedposition for releasably pinching-off the tube; a metering chamberdisposed between the occluders; and a fluid-actuated plunger having anopen position and a closed position for releasably compressing themetering chamber.
 107. The device of claim 106 further including anenergy storage tank in fluid communication with a fluid compressor forstoring compressed fluid under pressure.
 108. The device of claim 107wherein the fluid compressor intermittently provides compressed fluid tothe energy storage tank.
 109. The device of claim 108 further whereinthe pressure in the energy storage tank is increased over time.
 110. Thedevice of claim 107 further includes a pressure transducer in fluidcommunication with the energy storage tank and in electricalcommunication with the fluid compressor such that when high pressureoccurs the fluid compressor is switched off.
 111. The device of claim107 wherein the fluid compressor provides pressure to the energy storagetank and further wherein a second fluid compressor provides pressure tothe occluder.
 112. The device of claim 106 wherein the device isambulatory.
 113. The device of claim 106 further wherein thefluid-actuated chamber is connected to an energy storage tank that isinflated by a compressor.
 114. The device of claim 113 wherein theenergy storage tank is connected to an inflatable bladder.
 115. Thedevice of claim 106 wherein the fluid-actuated occluders includes asolenoid.
 116. The device of claim 106 wherein the fluid-actuatedplunger includes a pneumatic cylinder.
 117. The device of claim 106wherein the occluders are biased to a closed position.
 118. The deviceof claim 106 wherein the plunger is biased in an open position.